[iPad] Fullscreening a Youtube video while in Light Mode causes a white bar across the top and bottom of the screen
<rdar://problem/118530255>
Pull request: https://github.com/WebKit/WebKit/pull/20633
Committed 271535@main (634bc0b60bf0): <https://commits.webkit.org/271535@main> Reviewed commits have been landed. Closing PR #20633 and removing active labels.